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Dendroica palmarumpalm warbler

By Nicholas Laviola

Geographic Range

Dendroica palmarum breeds in the boreal forests of North America. This species breeds from northern Canada south through the northern United States. It is also classified as a neotropical migrant. On the East Coast, this species winters regularly from southern Delaware south through Florida and along the Gulf Coast through southern Texas. This species also winters throughout the West Indies, along the Yucatan Peninsula through Belize, and along coastal Honduras (Dunn and Garrett 1997; Wilson 1996).

Habitat

On the breeding grounds, Palm Warblers prefer open bogs with a wooded border of spruces and tamaracks. The bog cover is preferably Sphagnum moss, sedges, or other damp ground plants. On the wintering grounds, Palm Warblers prefer a variety of habitats including open and weedy fields, forest edges, second-growth, thickets, savannas, and mangroves (Dunn and Garrett 1997; Wilson 1996).

  • Terrestrial Biomes
  • taiga

Physical Description

Dendroica palmarum are average sized wood warblers (12.5 to 14.5 cm of length). In their basic plumage they present grayish-brown to olive-brown upperparts and yellowish to off-whitish underparts. Their have a long pale supercilium and bright lemony-yellow undertail-coverts. They present blurry brown streaking on breast and flanks and pale wing-bars. While in alternate plumage they present a rufous crown. Legs are blackish, eyes are small and black, and their bills are short and pointy, varying in color from black to pale.

There are two subspecies: 1) Yellow Palm Warbler in the east and 2) Western Palm Warbler. The Yellow Palm Warbler has underparts that are entirely yellow in all plumages. Western Palm Warbler only have deep yellow color in their undertail-coverts and throat, contrasting with a whitish or slightly yellow breast and belly. Sexes are very similar in both subspecies, and are often indistinguishable in the field (Pyle 1997; Wilson 1996).

  • Range mass
    9.65 to 10.63 g
    0.34 to 0.37 oz
  • Range length
    12.5 to 14.5 cm
    4.92 to 5.71 in
  • Average basal metabolic rate
    0.1554 W
    AnAge

Reproduction

Palm warblers are monogamous. However, there are two examples of bigamous males, where a second female was sometimes noted on territory. Pair formation in Palm Warblers begins shortly after arrival on breeding grounds, from late April until mid-May, where the male sings frequently upon arrival on breeding grounds.

Nest-building apparently begins in early to mid-May. The nest is usually located in Sphagnum of peat bog at the base of a small conifer on the ground. Site characteristics include nests closely located to the margins of heath bogs with scattered tall trees and small saplings, in addition to very dense shrub cover. The nest itself is cup-shaped and is comprised of weed stalks, grass and sedges, shreds of bark, rootlets, woody stems of Labrador tea, and bracken fern.

  • Breeding season
    May through July
  • Average eggs per season
    4
    AnAge
  • Average time to hatching
    12 days
    AnAge

Palm Warbler is known to produce only 1 clutch/season which consists of 4 to 5 eggs. Egg dates are from mid-May to late June, mid-July. The incubation period for this species is 12 days. During incubation, the male feeds the incubating female. Both parents feed the young in the nest and through fledging after 12 days of age (Wilson 1996).

Upon hatching, Palm Warblers are altricial and don't leave the nest for nearly a couple weeks. From juvenal plumage, Palm Warblers molt into their first basic plumage from July through September before winter sets in (Wilson 1996).

Lifespan/Longevity

The oldest recorded age for Palm Warbler is 6 years 7 months. There is no data on life span and survivorship.

Some body parasites found on Palm Warblers include ticks, mites, and Hippoboscid flies, which may affect their lifespan (Wilson 1996).

Behavior

Some common observed locomotion behaviors is that Palm Warbler commonly walks on the ground, wagging its tail.

Palm Warbler has also been observed behaving in an agonistic manner. Males chase and fight intruding males during breeding season and on wintering grounds. In a breeding territory, intruding males announce their presence by singing, but territory owners chase away the intruder and sing from a post to proclaim ownership (Wilson 1996).

Communication and Perception

Food Habits

On the breeding grounds, Palm Warblers are mainly insectivorous, taking food from the ground, from shrubs and scattered trees in the territory, and in the air by means of sallying from the ground or from a perch. In open areas, the majority of insects are caught from the ground or from low shrubs. Common insect prey include: grasshoppers (Odonata), beetles (Coleoptera), true files (Diptera), true bugs (Hemiptera), butterflies and moths(Lepidoptera) and wasp, bee and ant larvae (Hymenoptera). During the fall and winter, Palm Warblers feast on seeds, insects, and berries, including bayberries, in addition to nectar from century plants, sea grapes, hawthorns, and tiger claw trees (Wilson 1996).

Palm Warblers are diurnal visual foragers. Prey is captured by gleaning from leaves and cones, on the ground, and by hawking. Palm Warblers actively forage by flitting from branch to branch, as well as to the ground pursuing flying insects. Foraging methods are described as opportunistic, often switching between predation and nectivory.

  • Animal Foods
  • insects
  • Plant Foods
  • seeds, grains, and nuts
  • fruit
  • nectar

Predation

Gray Jays, Short-tailed Weasels and Garter Snakes have been reported as possible nest predators of Palm Warblers

(Wilson 1996).

Ecosystem Roles

Palm Warblers have very important roles in their boreal bog habitat. One of their most important roles in the ecosystem is by controling insect populations through feeding (Wilson 1996).

Economic Importance for Humans: Positive

Only known beneficial aspect of this species to humans is that Palm Warblers eat insects, thus may control the insect populations (Wilson 1996).

  • Positive Impacts
  • controls pest population

Conservation Status

Palm Warblers are tolerant of human activity, occurring in winter in residential areas.

One threat to Palm Warbler is the presence of TV towers and other tall structures. Palm Warbler is one of the most common victims to illuminated TV towers.

There seems to be no suggestion of degradation of habitat except for some evidence of bog drainage and peat-harvesting which may harm habitat (Wilson 1996).

Other Comments

Within the genus Dendroica, Palm warblers have been considered most closely related to Prairie, Kirtland's, and Pine Warblers, but more study is needed.

Palm Warbler is actually a misnomer, due to the fact that this species shows no inclination to use palms. Palms do dominate portions of where they overwinter (Dunn and Garrett 1997).

Contributors

Nicholas Laviola (author), University of Arizona, Jorge Schondube (editor), University of Arizona.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

taiga

Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

Dunn, J., K. Garrett. 1997. Warblers. New York: Houghton Mifflin.

Pyle, P. 1997. Identification Guide to North American Birds. Bolinas, California: Slate Creek Press.

Williams, W. 1996. Palm warbler. Pp. 1-20 in F Gill, A Poole, eds. The Birds of North America, No. 238. Washington, D.C.: Academy of Natural Sciences, Philadelphia, PA , and American Ornithologists Union.

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